The invention relates to a data processing system, comprising a main station (HS) and a peripheral station (PS) which are connected by a video line, the main station comprising a control unit with at least one processing unit, a memory, and a video control unit (VCU), the peripheral station comprising a video interface to which I/O apparatus is locally connected, an input of the video control unit being connected to the memory in order to form a composite video signal from the display information received for a video picture which is line-wise scanned, the VCU comprising first means for inserting data information from the memory into the composite video signal during at least one line duration during which the video picture has to be blanked, a video line (LDVI) which is connected on the one side to an output of said video control unit and on the other side to an input of the video interface, the peripheral station also comprising a display apparatus for a video picture which is line-wise scanned, said apparatus being connected to an output of said video interface, the video interface comprising second means for extracting said inserted data information from the composite video signal in order to make this data information available to a local data processing device which is also suitable for receiving further data information from the I/O apparatus present.
A system of this kind is known from the publication "Broadcast data in television", by A. J. Biggs and B. S. Barnaby, GEC Journal of Science and Technology, Vol. 41, No. 4, 1974, pages 117-124.
This article describes how data information can be added to television pictures by utilizing two picture lines during which the television picture is blanked. The data information in the form of a page consisting of 24 picture lines is stored in a memory of a transmitting station. This memory is cyclically read per data page and per television picture duration two lines of such a page are transmitted in a manner customarily used for television, said lines being stored in the local memory of the receiver device. This local memory is read per page, i.e. after 12 television picture durations. Such a memory in the receiver device substantially increases the price of the latter. The system is only suitable for receiving data information transmitted by the transmitting station.